Method and apparatus for routing signals through an optical network

Abstract

One embodiment of the present invention provides a system for routing signals through an optical network, wherein the optical network includes a plurality of optical cross-connects coupled together by a plurality of optical fiber links. Note that each of the optical cross-connects includes a plurality of non-blocking switches, and each optical fiber link can carry signals on a plurality of wavelengths. Upon receiving a request to establish a path, the system identifies a plurality of paths between the source and the destination through the optical network. Each switch in an optical cross-connect is associated with one or more wavegroups (wherein each wavegroup includes signals from one or more wavelengths). Note that each path through the optical network is comprised of wavelength/fiber links that belong to the same wavegroup, and that wavelength/fiber links that belong to the same wavegroup are routed through a non-blocking switch that is associated with the wavegroup. Next, the system calculates a cost for each of the paths based upon a cost function, and selects a path based upon the calculated costs.

What is claimed is:  
     
         1 . A method for routing signals through an optical network, wherein the optical network includes a plurality of optical cross-connects coupled together by a plurality of optical fiber links, wherein each optical cross-connect includes a plurality of non-blocking switches, and wherein each optical fiber link can carry signals on a plurality of wavelengths, the method comprising: 
 receiving a request to establish a path between a source and a destination;    identifying a plurality of paths between the source and the destination through the optical network;    wherein each of the plurality of paths is comprised of wavelength/fiber links that belong to the same wavegroup;    wherein wavelength/fiber links that belong to the same wavegroup are routed through the same non-blocking switch at each optical cross-connect;    calculating a cost for each of the plurality of paths based upon a cost function; and    selecting the path from the plurality of paths based upon the calculated costs.    
     
     
         2 . The method of  claim 1 , wherein each optical cross-connect in the plurality of optical cross-connects includes a single column of non-blocking switches.  
     
     
         3 . The method of  claim 1 , wherein the cost of a given path is a function of a number of hops in the given path and the utilization of wavelength/fiber links in the given path.  
     
     
         4 . The method of  claim 3 , wherein the cost of the given path is a function of the utilization of wavegroup links along the given path, wherein a given wavegroup link includes all wavelengths belonging to a given wavegroup on a given optical fiber link.  
     
     
         5 . The method of  claim 1 , wherein selecting the path involves selecting a primary path and at least one backup path from the plurality of paths.  
     
     
         6 . The method of  claim 1 , 
 wherein identifying the plurality of paths additionally involves considering paths that cross between wavegroups; and    wherein the cost of a given path that crosses between wavegroups includes an additional cost for switching between wavegroups.    
     
     
         7 . The method of  claim 1 , wherein identifying the plurality of paths involves using Djikstra's shortest path algorithm to find shortest paths based upon number of hops between the source and the destination.  
     
     
         8 . The method of  claim 1 , wherein identifying the plurality of paths involves identifying a plurality of link-disjoint paths.  
     
     
         9 . A computer-readable storage medium storing instructions that when executed by a computer cause the computer to perform a method for routing signals through an optical network, wherein the optical network includes a plurality of optical cross-connects coupled together by a plurality of optical fiber links, wherein each optical cross-connect includes a plurality of non-blocking switches, and wherein each optical fiber link can carry signals on a plurality of wavelengths, the method comprising: 
 receiving a request to establish a path between a source and a destination;    identifying a plurality of paths between the source and the destination through the optical network;    wherein each of the plurality of paths is comprised of wavelength/fiber links that belong to the same wavegroup;    wherein wavelength/fiber links that belong to the same wavegroup are routed through the same non-blocking switch at each optical cross-connect;    calculating a cost for each of the plurality of paths based upon a cost function; and    selecting the path from the plurality of paths based upon the calculated costs.    
     
     
         10 . The computer-readable storage medium of  claim 9 , wherein each optical cross-connect in the plurality of optical cross-connects includes a single column of non-blocking switches.  
     
     
         11 . The computer-readable storage medium of  claim 9 , wherein the cost of a given path is a function of a number of hops in the given path and the utilization of wavelength/fiber links in the given path.  
     
     
         12 . The computer-readable storage medium of  claim 11 , wherein the cost of the given path is a function of the utilization of wavegroup links along the given path, wherein a given wavegroup link includes all wavelengths belonging to a given wavegroup on a given optical fiber link.  
     
     
         13 . The computer-readable storage medium of  claim 9 , wherein selecting the path involves selecting a primary path and at least one backup path from the plurality of paths.  
     
     
         14 . The computer-readable storage medium of  claim 9 , 
 wherein identifying the plurality of paths additionally involves considering paths that cross between wavegroups; and    wherein the cost of a given path that crosses between wavegroups includes an additional cost for switching between wavegroups.    
     
     
         15 . The computer-readable storage medium of  claim 9 , wherein identifying the plurality of paths involves using Djikstra's shortest path algorithm to find shortest paths based upon number of hops between the source and the destination.  
     
     
         16 . The computer-readable storage medium of  claim 9 , wherein identifying the plurality of paths involves identifying a plurality of link-disjoint paths.  
     
     
         17 . An apparatus for routing signals through an optical network, wherein the optical network includes a plurality of optical cross-connects coupled together by a plurality of optical fiber links, wherein each optical cross-connect includes a plurality of non-blocking switches, and wherein each optical fiber link can carry signals on a plurality of wavelengths, the apparatus comprising: 
 an identification mechanism that is configured to identify a plurality of paths between a source and a destination through the optical network;    wherein each of the plurality of paths is comprised of wavelength/fiber links that belong to the same wavegroup;    wherein wavelength/fiber links that belong to the same wavegroup are routed through the same non-blocking switch at each optical cross-connect;    a calculating mechanism that is configured to calculate a cost for each of the plurality of paths based upon a cost function; and    a selection mechanism that is configured to select the path from the plurality of paths based upon the calculated costs.    
     
     
         18 . The apparatus of  claim 17 , wherein each optical cross-connect in the plurality of optical cross-connects includes a single column of non-blocking switches.  
     
     
         19 . The apparatus of  claim 17 , wherein the cost of a given path is a function of a number of hops in the given path and the utilization of wavelength/fiber links in the given path.  
     
     
         20 . The apparatus of  claim 19 , wherein the cost of the given path is a function of the utilization of wavegroup links along the given path, wherein a given wavegroup link includes all wavelengths belonging to a given wavegroup on a given optical fiber link.  
     
     
         21 . The apparatus of  claim 17 , wherein the selection mechanism is configured to select a primary path and at least one backup path from the plurality of paths.  
     
     
         22 . The apparatus of  claim 17 , 
 wherein the identification mechanism is configured to consider paths that cross between wavegroups; and    wherein the cost of a given path that crosses between wavegroups includes an additional cost for switching between wavegroups.    
     
     
         23 . The apparatus of  claim 17 , wherein the identification mechanism is configured to use Djikstra's shortest path algorithm to find shortest paths based upon number of hops between the source and the destination.  
     
     
         24 . The apparatus of  claim 17 , wherein the identification mechanism is configured to identify a plurality of link-disjoint paths.